1. Field of the Invention
This invention relates generally to a method and a system for cooling a heat load, and more particularly to a method and a system for cooling a heat load utilizing direct contact between a liquid coolant and a refrigerant which may be operated in any orientation and under any gravitational situation.
2. Brief Description of the Prior Art
Applications for refrigeration systems have steadily increased and become more demanding. Currently, aerospace refrigeration systems are needed which can provide cooling in situations where there is zero gravity or high gravity or when in any orientation. Additionally, refrigeration systems are needed which are smaller and lighter.
Disclosed in U.S. Pat. No. 4,078,392 (hereinafter '392) issued to Mark O. Kestner on Mar. 14, 1978 is a refrigeration system that utilizes direct contact heat transfer between a refrigerant and a magnetic coolant. The coolant absorbs the cooling load and the refrigerant chills the coolant by direct mixing such that the refrigerant is vaporized. However, the system requires that the fluids be immiscible so that they may be separated by using buoyancy forces and that the first fluid be ferromagnetic so as to allow their separation to be assisted by a magnetic field. Also, the mixing and the separation of the fluids occur within the same system component and gravity is required for correct system performance. Furthermore, the '392 system requires a two-phase condenser which is orientation-dependent.
A method of refrigeration is disclosed by S. G. Sylvan in U.S. Pat. No. 3,277,659 which issued on Oct. 11, 1966. The refrigeration method utilizes two fluids, a refrigerant and a coolant. The liquid coolant is injected into the refrigerant gas before its entry into the compressor to allow isothermal compression. However, only the refrigerant absorbs or rejects heat and the method still utilizes the conventional condensing and evaporating steps which require gravity in order to separate the liquid and the gas refrigerant.
An additional refrigeration method and system is disclosed by Michael St. Pierre in U.S. Pat. No. 4,689,964 (hereinafter '964) which issued on Sept. 1, 1987. The refrigeration method and system of the '964 patent is operable in zero gravity situations and achieves its cooling by the circulation of two different refrigerants within its system. However, the two refrigerants both boil and condense inside of the two-phase heat exchangers which are orientation-dependent in the refrigeration system of the '964 patent. Additionally, a separate refrigerant oil is necessary to provide lubrication to the system's components.
The heat pump cycle disclosed by Reinhard Radermacher in U.S. Pat. No. 4,724,679 (hereinafter '679) which issued on Feb. 16, 1988 utilizes a combination of two refrigerants for circulation within the system. The refrigerants are required to have widely different boiling points so that one of the refrigerants does not boil, but remains a liquid throughout the system. The system and method disclosed in the '679 patent, however, requires the use of two soluble fluids and thus the selection of applicable circulating refrigerants is limited to those which are completely soluble in one another. The system requires heat to be added in the desorber in order to vaporize the refrigerant and to cool the heat load. The desorber, though, is a two-phase device which is highly dependent on orientation. Additionally, the heat pump cycle disclosed in the '679 patent requires gravity to operate the adsorber, a two-phase heat exchanger, so that only liquid exits the adsorber instead of gas which would exit if the adsorber were inverted. Thus, the heat pump cycle can not properly function in all orientations.
It would be desirable to develop a refrigeration system which could operate in zero gravity or high gravity situations, as well as a system which could utilize one of its circulating components, which may be completely or partially soluble or totally insoluble in the other component, to provide lubrication so as to forego the use of a separate refrigerant oil. It would also be desirable to cool one or many heat loads with one of the system's components which would remain liquid so as to reduce the likelihood of gaseous leaks since a liquid is more reliably contained under pressure. Furthermore, it would be desirable for a refrigeration system to be designed so as to be lightweight and to maintain the minimum system pressure necessary for increased efficiency.